This invention relates in particular to cutting devices for use in association with sewing machines and in particular to a new and useful device for aligning and cutting lengths of material which have thickened portions separated by thin portions.
The invention relates to a device for aligning and cutting lengths of material. A device of this kind is to be found in French Pat. No. 1,374,528. For aligning the pileless rows of lengths of terrycloth straight along the woof thread, the prior art device has two plates that can be pressed against the lengths of material, which plates can be moved in opposite directions to one another by means of a motor, two reciprocally meshing gears, and rods which are each connected to a gear. On each plate is an aligning ledge and a supporting ledge, both of which can be pivoted jointly, also in opposite directions, by means of an electromagnet. Between the two plates is a cutting device that operates transversely to the direction of feed of the length of material, with its cutting plane lying exactly in the plane of symmetry of the pair of ledges.
A sensor device that detects the thickness of the length of material is positioned ahead of the alignment and cutting station. With the aid of the signals produced by detection of the front and rear pile edges of a pileless row, making allowance for the distance between the sensor device and the cutting plane of the cutting device, the drive mechanisms of the two pairs of ledges and the two plates are controlled so that the plates and the pair of ledges engage with the length of material precisely at the point in time when the pileless row is exactly even with the cutting plane.
Thus, to achieve the desired result of cutting the length of material straight along the thread and exactly down the middle of a pileless row, with the prior art device it is necessary to have the alignment tools engage with the length of material precisely symmetrically to the desired cut line, for which purpose not only the aforementioned sensor device but also a cam wheel drivable at two different rpm speeds are required.
The invention provides simple means for aligning a length of terrycloth for cutting down the middle of a pileless row.
By reciprocal coupling of the paired aligning and supporting ledges and the support piece for the cutting device by means of a parallelogram frame, when the distance between the pairs of ledges changes, the support piece is always moved simultaneously half the change in distance. Since the cutting device is positioned on the support piece in such a way that its cutting plane is exactly in the center between the two pairs of ledges, this central position of the cutting device is maintained regardless of the distance between the two pairs of ledges. Because of this movement ratio, therefore, in order to accomplish the alignment, all that is required is to stop the length of material with the pileless row in the area of the two alignment ledges and to move the two pairs of ledges, before engagement with the length of material, so close to one another that the two aligning ledges set down into the pileless row. When the pairs of ledges are then moved away from one another until the aligning ledges lie right up against the pile edges and have in the aligned the length of material straight along the thread in the area of the pileless row, upon completion of alignment of the cutting plane of the cutting device is autmatically situated precisely in the middle of the pileless row, so that cutting can take place immediately after alignment.
A further simplification is achieved in that only one pair of ledges is capable of movement paralled to the plane of the length of material. By performing the alignment movement with the front alignment ledge and front support ledge with respect to the direction of feed of the length of material, so that the alignment movement is counter to the direction of feed of the length of material, the additional advantage is gained that any shifting or wrinkling that may occur upon alignment occurs only in the segment of material lying on the supply side of the cutting line and is smoothed out again by the subsequent process of moving the length of material forward.
Accordingly it is an object of the invention to provide an improved device for centering a cuttng between two aligning ledges which are aligned with spaced apart edges of material so that the cutter will be centered between the aligning ledges for cutting the material between the edges with which the plates are aligned.
A further object of the invention is to provide a material cutting device which is simple in design, rugged in construction and economical to manufacture.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which a preferred embodiment of the invention is illustrated.